Antitumor antibiotic produced by an unidentified species of Streptomyces from Peruvian soil: Dion et al., J. Am. Chem. Soc. 78, 3075 (1956); Ehrlich et al., Antibiot. Chemother. 6, 487 (1956). Several methods of synthesis: De Wald, Moore, ibid. 80, 3941 (1958); eidem, US 2965634 (1960 to Parke, Davis). Review: Pittillo, Hunt, Antibiotics vol 1, D. Gottlieb, P. D. Shaw, Eds. (Springer-Verlag, New York, 1967) pp 481-493.